Take a look into those beautiful green eyes. They’ll tell you how your cat is feeling and whether she’s in a good mood or angry about something. But they’re also the eyes of a predator. Everything about your cat’s eyes is designed to help her hunt efficiently.
Cats’ eyes and humans’ have one thing in common. Because our eyes are on the fronts of our heads, we both have good depth perception and peripheral vision. But that’s where the similarity ends.
Our eyes have six times more cones than cat eyes do, while cats’ eyes have many more rods, the retinal cells that work well in dim light but don’t allow for much color differentiation. And cats have a reflective layer in the back of the retina known as a tapetum lucidum. That’s what gives their eyes that eery flash when struck by light in the dark. Light reaching the eyes bounces back from the tapetum lucidum, giving the retina another chance to get a look at things.
Because cats’ eyes are designed for seeing at night, their pupils constrict into narrow slits during the day to prevent too much light from entering the retina.
Designed For Hunting
If you hold a toy right in front of your cat’s face, chances are he won’t respond because he can’t see it very well. Cats are nearsighted and objects look blurry closeup. According to the website, Cat-Health-Detective.com, a cat’s sharpest vision is about six to 20 feet away. To help the cat zero in on its prey, the field of vision in one eye partially overlaps the field of vision in the other. The eye interprets these slightly different views as a three dimensional image, so the cat can judge the distance between himself and the tiny animal (or toy) he wants to catch.
And all those rods? In addition to helping the cat see in dim light, they serve as motion detectors, letting the cat know when danger, or a better opportunity, is approaching from either side.
That Third Eyelid
You’ve heard about a cat’s third eyelid, and maybe you’ve even seen it when your cat was sick. Writing for Scientific America, veterinarian Paul Miller says it “plays an important role in maintaining the health of the eye surface.”
The third eyelid, Miller says, is really a fold of tissue covered by the conjunctiva, a specialized mucous membrane that faces the inner surface of the eyelids and the cornea. It’s home to a dense population of lymphoid follicles that trap dirt and keep it out of the eye itself. It also protects the cornea as cats move through tall grass, Miller says.
Window On Her Emotions
Your cat’s eyes can tell you a lot about her mood. If her pupils are fully dilated, she’s probably frightened. Narrow slits can indicate anger. Blinking is catspeak for, “I trust you.” And half-closed eyes are the sign of a relaxed cat who’s ready for a nap.
Signs Of Illness
Your cat’s eyes can also tell you how she’s feeling. Red, runny eyes and an elevated third eyelid are both signs that your cat may be sick and should see a veterinarian. Other signs of eye problems include white eyelid linings, crusty gunk in the corners of the eyes and cloudiness or change in eye color. Closed eyes indicate the eyes are painful.
Like humans, cats can suffer from glaucoma, cataracts or a detached retina. These may be related to another disease, such as diabetes or high blood pressure, and may resolve when the underlying condition is treated. Other cat eye disorders include
- Conjunctivitis: The cat’s eyes will be red and swollen and may be runny. It is often a symptom of an upper respiratory infection or herpes. The usual treatment is ointment or eye drops.
- Keratitis: This inflamation of the cornea causes the cat’s eyes to look cloudy and watery.
- Bulging eye: Trauma, an accident or an eye tumor can cause a cat’s eye to bulge.
- Blindness or partial loss of vision: Cats can lose their eyesight when light-sensitive cells at the back of the eye degenerate.
Fact And Fiction
It’s a myth that cats can see in total darkness. They need at least some light to be able to find their way to that basement litter box or hiding place. If your litter box is in the basement, night lights will make it easier for your cats find their way to the “bathroom” in the middle of the night.
It’s also a myth that cats are color blind. In some studies, cats’ eyes responded to colors in the purple, blue, green and yellow ranges but probably saw red, orange and brown in shades of gray. The website Katzenzeitung describes a cat’s vision as seeing a “world colored in fuzzy pastels.”